Method of applying windows to envelopes and bags

ABSTRACT

A blank for making an envelope with a window opening is fed past a first station where a volatile solvent, such as ethylene trichloride, is applied to the underside of the blank to penetrate and partly or completely saturate the blank around the window opening. Then a strip of a transparent material, such as polystyrene, which is slightly larger than the window opening is pressed onto the blank over the opening. The portion of the strip overlying the blank around the opening is dissolved momentarily by the solvent and adheres completely around the opening. Alternatively, the solvent can be applied after the strips are placed over the window openings. Alcohol may be added to the solvent to increase the speed and depth of penetration of the solvent.

United States Patent [1 1 Taylor 51 Jan. 9, 1973 [54] METHOD OF APPLYING WINDOWS TO ENVELOPES AND BAGS [52] US. Cl. ..l56/l08, 156/308, 229/71 [51] Int. Cl. ..B60j 9/00 [58] Field of Search ..l56/108, 306, 307, 308, 442;

282/115 R, 25, DIG. 2; 229/71; 93/61, 66

[56] References Cited UNITED STATES PATENTS 2,690,102 9/1954 Halahan et al ..l56/l08 X 2,827,671 3/1958 Martin ..156/l08 X 2,859,550 11/1958 Langan.... ..156/108 X 3,442,730 4/1969 Deitz ..l56/308 X Primary Examiner-Carl D. Quarforth Assistant Examiner-P. A. Nelson Attorney-Shlesinger, Fitzsimmons & Shlesinger [57] ABSTRACT A blank for making an envelope with a window opening is fed past a first station where a volatile solvent, such as ethylene trichloride, is applied to the underside of the blank to penetrate and partly or completely saturate the blank around the window opening. Then a strip of a transparent material, such as polystyrene, which is slightly larger than the window opening is pressed onto the blank over the opening. The portion of the strip overlying the blank around the opening is dissolved momentarily by the solvent and adheres completely around the opening. Alternatively, the solvent can be applied after the strips are placed over the window openings. Alcohol may be added to the solvent to increase the speed and depth of penetration of the solvent.

7 Claims, 4 Drawing Figures METHOD OF APPLYING WINDOWS TO ENVELOPES AND BAGS This invention relates to envelopes and bags, and more particularly to a novel method of securing transparent windows over the openings in conventional window-type business envelopes.

Heretofore it has been the practice to use an adhesive for sealing the transparent window strip over the openings in window-type business envelopes. This adhesive is usually applied to the inside of each envelope around the window opening; and the transparent plastic window is then spaced over the adhesive to secure the window to the envelope. With this method of fastening the window in place, it is essential that only a limited amount of adhesive be used, and that the adhesive be carefully applied to an area spaced from the edge of the opening in the envelope, so that the adhesive will not squeeze out from under the edge of the window and form unsightly smears on the portion of the transparency registering with the opening. Similar caution must also be taken to prevent the adhesive from squeezing out beyond the outer edge of the transparency onto the envelope blank itself, because in such case opposite sides of the envelope may become glued to one another.

By taking such precautions, however, there is always the danger that the adhesive will be applied to the blank only in an area spaced from the edge of the opening, with the result that the marginal edge of the envelope around the opening may not be fully adhered to the window. Consequently, the window may easily be accidentally peeled from the blank or be bent backwardly so that it interferes with automatic handling or machine-loading of the envelopes. Moreover, where the window is not secured over its whole overlapping area to the confronting portion of the envelope blank, the envelope might buckle or distort, making automatic processing and handling difficult, if not impossible.

Attempts have been made to achieve one hundred per cent adherence of the marginal edge of a window around an opening in an envelope, but prior methods have been extremely slow and exacting.

It is an object of this invention to provide a novel method for rapidly and completely sealing a transparent window over a window opening in an envelope, or over a window opening in a web from which an envelope or a bag is to be made.

A more specific object of this invention is to provide a novel method of applying windows to business envelopes and to webs for forming envelopes and bags in such manner that each window is fully secured to the envelope or web completely around the opening in the envelope or web and around the marginal edge of the window itself.

Another object of this invention is to provide a method which permits transparent windows to be secured over openings in envelopes and webs of the type described without the use of an adhesive.

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawing.

IN THE DRAWING FIG. 1 is a plan view of an unfolded paper envelope blank having a window opening therein over which a transparent window has been secured in accordance with this invention;

FIG. 2 illustrates schematically the method and part of the apparatus employed for sealing windows to envelopes in accordance with one embodiment of this invention;

FIG. 3 illustrates schematically the method-and part of the apparatus for securing windows to envelopes in accordance with a further embodiment of this invention; and

FIG. 4 is an enlarged sectional view taken along the line 4-4 in FIG. 3 looking in the direction of the arrows.

Referring now to the drawing by numerals of reference, 10 denotes a conventional paper envelope blank, which has an elongate, generally rectangular window opening 12 (FIG. 1) therein. A rectangular strip 14 of transparent plastic material is secured over opening 12 against the inside of the blank to form the window of the envelope.

The strip 14 may be made, for example, from transparent polystyrene, which is soluble in ethylene trichloride. FIGS. 2 and 3 illustrate two different methods of securing windows to envelope blanks in accordance with this invention.

In the method of FIG. 2, the envelope blanks 10, to which the transparent windows are to be attached, are gripped or supported adjacent their marginal side edges by conventional conveyor means (not illustrated), and are fed one by one, and in spaced relation, between a pair of cooperating rollers or drums 16 and 17. Roll 17 is an applicator roll having an engraved or felt peripheral surface and a length slightly greater than the length of the window opening 12. It extends beneath the level L of a supply of a solvent, such as ethylene trichloride, held in the container 18. As the roll 17 rotates, its peripheral surface constantly picks up the solvent from the container 18 and applies the solvent to the underside of each blank around its opening 12, to saturate the area around the opening 12 with the solvent. Excess solvent is wiped from the roll 17 by a conventional wiper 19 before the applicator roll engages and saturates the undersides of the blanks 10 with the solvent. The upper roll 16 is merely a back-up roll used to help press the blanks 10 against the applicator roll 17.

Each of the rolls 16 and 17 may have an axial length which is less than the overall width of a blank 10, but which must be at least equal to or greater than the width of a strip 14, so that as the blanks 10 pass between the rolls l6 and 17, at least the portions A thereof (FIG. I) will be saturated with the solvent.

While still wet, the blanks 10 then pass between a conventional vacuum roll 21 and its registering backup roll 22. Above the roll 21 a continuous strip S of transparent plastic window material such as polystyrene is fed in a conventional manner through a guide 22 and beneath a reciprocating knife 23, which cuts the strip S into individual strips 14, which are delivered by vacuum drum or roll 21 onto the upper surfaces of the saturated blanks 10 in registry with the openings 12 therein. Since the vacuum drum 21 and assoeiated means for effecting delivery of the severed strips 14 into registry with the openings in the blanks are conventional, they need not be described in further detail herein.

As each strip 14 is conveyed between the drums 21 and 22 and into contact with the marginal portions of the opening 12 in a blank 10, the solvent in the nowsaturated blank momentarily dissolves the confronting surface of the strip 14, so that when the combined blanks and strips pass from between the drums 21 and 22, each strip 14 will be fused and secured to a blank 10 all the way around the opening 12 therein, as well as around the marginal edge of the strip itself.

In executing the method disclosed in FIG. 2, the solvent is applied to the underside of the blank 10, while the strip 14 is applied to the upper or opposite side of the blank. This is possible because the ethylene trichloride soaks rapidly through the blanks as it is applied thereto by the roll 17; and consequently, by the time a blank reaches the rolls 21 and 22, the solvent has penetrated through the blank to the upper surface thereof. Since ethylene trichloride is extremely volatile, it evaporates very rapidly from the blank 10. The dissolved portion of the plastic strip will adhere to the paper blank 10 uniformly and completely around the opening 12, so that neither the edge of the opening 12 nor the outer edge of the strip 14 will peel back or otherwise bend outwardly to interfere with automatic loading or handling of the envelope either in its blank or final form.

It has been found that in certain circumstances this operation can be improved by adding alcohol to the ethylene trichloride solvent. When this mixture is applied by the roll 17 to the blanks 10, it penetrates faster than when ethylene trichloride alone is employed; and this mixture also effects a deeper penetration of the dissolved polystyrene into the blank proper, so that the adhesion between the strip 14 and the blank 10 is improved.

In the embodiment illustrated by FIGS. 3 and 4, the blanks 10 are fed between a vacuum roll 21, which is similar to the vacuum roll illustrated in FIG. 2, and an associated back-up roll 22. As in the previous embodiment, a reciprocating knife blade 23 severs strips 14 of polystyrene from a supply S thereof; and the drum 21 then conveys these strips one by one onto successive blanks 10 so that each strip is positioned over the window opening 12 in the blank.

Immediately after passing from between the drums 21 and 22, each blank 10, with a strip 14 thereon, passes between an applicator roll 30 and an associated back-up roll 31. One or more rectangular, hollow applicator frames or bosses 32 (FIG. 4) project from the periphery of the roll 30 for immersion, as the roll 30 resolves, beneath the level L of a supply of ethylene trichloride in a container 34 positioned beneath the roll 30. After passing through the solvent, the frames or bosses 32 rotate into engagement with the undersides of successive blanks 10, so that the underside of each blank is saturated by one of the bosses 32 in an area that registers with the marginal portion of the overlying strip 14. As in the first embodiment, the solvent penetrates each blank to melt or fuse the confronting surface of the overlying strip 14 to adhere it to the blank.

As shown in FIG. 4, each boss or frame 32 has a configuration generally similar to the area bounded by the edge of the opening 12 in a blank 10, and the surrounding peripheral edge of the attached strip 14. However, to prevent the applicator 30 from applying solvent through an opening 12 and directly onto an overlying strip 14, and thus damaging the window, each frame 32 is made slightly narrower than the portion of the blank surrounding the window opening so that the inner and outer peripheral surfaces of each frame 32 will be spaced slightly outwardly from the edge of each opening 12, and slightly inwardly from the outer edge of the associated overlay or window strip 14 at the time that the boss is pressed against a blank. The solvent, being in liquid form, will be drawn by capillary action to the edge of the associated opening 12 and outwardly toward the outer marginal edge of the overlying strip 14 to effect complete seal of the strip to the blank. This assures that each strip 14 will become fully bonded to each envelope blank.

In this second embodiment, alcohol may also be added to the ethylene trichloride solvent in order to produce a deeper and more rapid penetration of the blank.

While the invention has been described and illustrated specifically in connection with the production of window envelopes from envelope blanks, it will be understood, as already indicated, that it may be used also in the production of both envelopes and bags from webs which have spaced window openings therein. In fact, the invention may be used also in the production of pasteboard and thin gauge cardboard boxes with windows. In the production from webs of envelopes, and/or bags, and/or pasteboard or thin cardboard containers with windows, the web, from which the envelopes or bags or pasteboard or cardboard containers is to be made, may be first perforated or stamped to form window openings, and may then be passed between a doctor roll 17 and a back-up roll 16 so that the doctor or applicator roll 17 will apply the ethylene trichloride or other solvent around the successive window openings in the web, as in the embodiment illustrated in FIG. 2; and then the window strip 14 will be fed over the successive window openings of the traveling web by roller 21, and adhered thereto by passage of the web between the opposed rollers 21 and 22. The webs, from which window envelopes and/or bags, and/or the pasteboard or cardboard containers with windows, are to be formed, may also be first perforated to provide the window openings, and then the solvent may be applied around the window openings by feeding the perforated web between rolls 21 and 22, as illustrated in FIG. 3, to apply the window strips 14 over successive window openings of the web, and then applying solvent around these openings by means of applicator frames or bosses 32 to adhere the window strips to the openings in the envelope, bag, pasteboard or cardboard web.

Of course windows can be applied to bag, pasteboard or cardboard blanks in the same manner as they are applied to the envelope blanks in the modifications of this invention illustrated in FIGS. 2 and 3.

From the foregoing it will be apparent that applicant has developed an extremely economical and reliable method of completely sealing windows to envelopes,

bags, pasteboard and cardboard containers and the like. Although in the method illustrated in FIG. 2 the solvent is applied to the side of the blank remote from the window material, it may, of course, be applied to the side of the blank onto which the window is subsequently deposited, if desired. The first mentioned alternative is not available in methods which utilize an adhesive.

Applicants process is readily adaptable to existing equipment; but the process eliminates need for any separate adhesive or for previous preparation of the area where adhesion is to take place. Also the method requires no heat to effect adhesion; it is extremely fast; and it effects 100 percent adherence without any squeeze-out of adhesive around the window perimeter. It thus obviates the need to wash away undesirable adhesive deposits. The ethylene trichloride solvent dries extremely rapidly, and can even be applied to printed blanks without any worry of eradicating, smearing or obliterating the printed matter. Also, the adhesive action can be controlled precisely by using alcohol in the solvent to increase or decrease the penetration of the fused window material into the window blank or web. In addition, faulty business envelopes, for example, the type wherein the transparent windows are not fully sealed to the envelopes, can be repaired readily by inserting over the window in each envelope a strip of polystyrene that is slightly larger than the faulty window, and then applying the solvent to the exterior of the envelope around the window opening to fuse the strip around the marginal edge of the faulty window.

While polystyrene has been mentioned as the preferred material for the window, and ethylene trichloride as the preferred solvent therefor, it will be understood that other suitable transparent, plastic materials may be used for the windows of the envelopes providing a solvent is available which will fuse the material over its whole overlapping area to the envelope. In this connection, it is to be understood that applicant does not restrict himself to the use of ethylene trichloride as a solvent, since aromatic hydrocarbons, chlorinated hydrocarbons and esters thereof, that is, other olefinic halide solvents may also be used as, for instance, ethylene dichloride, ethylene dibrornide, etc.

Having thus described my invention, what I claim is: 1. The method of making an envelope, bag, pasteboard or cardboard container and the like from a blank, or web having a window opening therein, which comprises placing a transparent strip, which is made of a plastic that when subjected to a solvent therefor becomes adhesive, and which is larger than the window opening, over said opening so that marginal edges of the strip overlap the blank around said opening,

saturating the side of the blank opposite said strip with a volatile solvent for the strip, and pressing said overlapping portion of said strip against the saturated area to cause said solvent to contact and to dissolve the portion of the strip around said opening and consequently to fuse and adhere the overlapping portion of said strip around said opening to the blank. 2. The method as defined in claim 1, wherein said solvent is applied to the blank before the strip is placed over said opening.

3. The metho as defined in claim 1, wherein the solvent is applied after said strip is placed over said openmg.

4. The method as defined in claim 1, wherein said solvent is applied simultaneously with the pressing of said strip against said area.

5. The method defined in claim 1, wherein said solvent is selected from the group consisting or aromatic hydrocarbons, chlorinated hydrocarbons, and esters thereof, and said strip is made from polystyrene.

6. The method as defined in claim 5, wherein said solvent is ethylene trichloride.

7. The method as defined in claim 5 wherein said solvent comprises a mixture of alcohol and ethylene trichloride. 

2. The method as defined in claim 1, wherein said solvent is applied to the blank before the strip is placed over said opening.
 3. The method as defined in claim 1, wherein the solvent is applied after said strip is placed over said opening.
 4. The method as defined in claim 1, wherein said solvent is applied simultaneously with the pressing of said strip against said area.
 5. The method defined in claim 1, wherein said solvent is selected from the group consisting or aromatic hydrocarbons, chlorinated hydrocarbons, and esters thereof, and said strip is made from polystyrene.
 6. The method as defined in claim 5, wherein said solvent is ethylene trichloride.
 7. The method as defined in claim 5 wherein said solvent comprises a mixture of alcohol and ethylene trichloride. 